Since Kurt is out of the office, I'll add a bit to this. Hopefully, he won't mind. Ultimately, his shop (the ODWC Fisheries Research Lab) administers the lake record program, so they will have the final word.
I broached this subject recently and was informed that the tailwaters of a dam (first 1000 feet) are typically lumped with the lake. Yes, in a series of lakes (such as Grand, Hudson, and Ft. Gibson), one would think a fish caught below Grand would be a Hudson Lake fish. Maybe Kurt can clarify this decision process.
As for the river above a lake, it may come down to the ecology of the species and how they use the river or lake which may factor into the decision. While the program is administered by OFRL, these lake records are individually approved or denied by the regional fisheries biologists. If they feel the lake record is valid, they approve it at their discretion.
ODWC Paddlefish Biologist
E-Check your paddlefish harvest HERE